1. Carlson, J., Green, M., Griffiths, P., Harris, J.: Infinititesimal variations of Hodge structures. Compos. Math.50, 109?205 (1983)
2. Green, M.: A new proof of the explicit Noether-Lefschetz theorem. Preprint
3. Griffiths, P., Harris, J.: On the Noether-Lefschetz theorem and some remarks on codimension two cycles. Math. Ann.271, 31?51 (1985)
4. Lopez, A.: Brown University Ph. D. thesis, 1988
5. Sernesi, E.: Topics on families of projective schemes. Queen's Pap. Pure Appl. Math.73 (1986)